Van de Kamp, Peter (1901–1995)

Dutch-American astronomer, director of Sproul
Observatory, and pioneer in the search for extrasolar
planets. In 1937, using a technique brought to Sproul by Kaj A. Strand,
he initiated a search for unseen companions of 54 stars known to lie within
16 light-years (5 parsecs) of the Sun (see stars,
nearest). Over the next two decades, the Sproul group, which also included
Sarah Lee Lippincott, reported evidence
for planetary bodies around several of the target stars, including 61
Cygni, Ross 614, and Lalande 21185.
In 1963, van de Kamp claimed that a giant planet, about 11 times the mass
of Jupiter, was in a 24-year orbit around
Barnard's Star,1 a stellar
neighbor of the Sun in which he had a special interest. Over the next few
years, he published further evidence for unseen companions around other
nearby stars. However, doubts began to grow among fellow astronomers about
the validity of his data. In particular, Robert Harrington pointed out that
all of the "wobbles" supposedly caused by van de Kamp's planets were of
an identical form, suggesting a systematic instrumentation effect. Undeterred,
van de Kamp further analyzed his data on Barnard's Star and, in 1976, claimed
he now had evidence for two companions – a 0.7 Jupiter-mass planet
with a period of 12 years and a 1.2 Jupiter-mass planet with a period of
26 years, orbiting at distances of 3 and 5 times that of the Earth from
the Sun, respectively. Three years earlier, he suggested that the nearby
Sun-like star, Epsilon Eridani, had a planetary
companion 6 times as massive as Jupiter. Though the planetary discoveries
claimed by van der Kamp and his contemporaries at Sproul were all subsequently
rejected, van der Kamp's optimism in general has been vindicated. In a 1963
article he argued that there was no reason to doubt the existence of "large
numbers" of extrasolar bodies larger than Jupiter and smaller than stars.
Recent confirmation of the existence of giant planets and brown
dwarfs beyond the Solar System have vindicated that view.2, 3